Modeling
B. Ghasemi; A. Hemmat; A. Ghasemi; A. Habibi Rad
Abstract
Introduction: Apple is one of the most important horticultural crops of Iran. Its production in the country stands in the second place after citrus. Iran holds the fourth place in the world production of apples and gains a major share in the export of this product. Therefore, it is necessary to enhance ...
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Introduction: Apple is one of the most important horticultural crops of Iran. Its production in the country stands in the second place after citrus. Iran holds the fourth place in the world production of apples and gains a major share in the export of this product. Therefore, it is necessary to enhance the quantity and quality of the fruit in order to maintain and promote its position among the countries importing this product from Iran. Most of the mechanical damages to fruits and vegetables occur due to contact stresses under static, quasi-static and impact loading. To obtain stress distribution inside the fruit we can use finite element analysis. The aim of this study was to simulate the behavior of the apple as a viscoelastic body subjected to quasi-static loading and also to determine the failure criteria (maximum normal stress or shear stress) of apple flesh to estimate its susceptibility to mechanical bruising.Materials and methods: In this study, Golab kohanz apple was used. Two samples were removed from each apple using a core sampler, one was used for uniaxial compression and the other was used for confined compression test using Instron universal tension and compression machine. Spherical indenter and parallel plate tests were performed in order to study apple susceptibility to bruising at four deformation levels (1, 2, 3 and 4 mm) and the bruise volume was then measured after 24 hours. Stress-strain curves were plotted and then, the elastic and viscoelastic properties were obtained. Then, by using the data obtained from apple properties, the apple was modeled in Abaqus software as spherical and cylindrical shapes with viscoelastic behavior subjected to quasi-static loadings.Results and Discussion: The normal stress distribution of the modeled apple in the shape of a cylindrical sample is shown in Fig. 4. The value of maximum normal stress was obtained (0.51 MPa) at the contact point of the loading plate with the sample. Experimental and modeled stress-strain curves are shown in Fig. 5. Up to the bio-yield point, the two curves are nearly matched; and beyond that point, there are some overestimations in the predicted stress values. The location and pattern of failure have often been used to explain the cause of failure in fruits. When specimens of fruit are subjected to a uniaxial compression, the failure often occurs the maximum shear stress plane. Failure patterns in the tested samples indicate that the failure occurs due to shear stresses. Another explanation that has been used by researchers for shear failure is the bruising position inside the fruit after loading. The position of bruising in most of the tested apples was a distance away from the apple surface (Fig. 7).According to the experiments results at the three deformation levels of 2, 3, and 4 mm, the maximum generated normal stress inside the apple was above the point of failure of the cylindrical samples. Based on the empirical results, the bruising was almost zero for the apples subjected to one or two mm deformation (Fig. 9a). The experimental value of the shear strength of the Golab kahanz apple was obtained to be 0.23 MPa. The maximum shear stress inside the modeled apple due to the two mm deformation was 0.195 MPa, which was lower than the shear strength of the apple. On the other hand, by applying three and four mm of deformation, the maximum shear stresses were obtained to be 0.24 and 0.26 MPa, respectively, indicating that the induced stress exceeded the shear strength of apple flesh; therefore, the bruising was observed in the flesh of these apples. The location of the maximum shear stress corresponds to the location of bruising in the tested samples as shown in Fig. 9b.According to the obtained results from the modeling in the finite element software, we can use this software in order to recognize and investigate the damages in agricultural products during different loading conditions (Harvesting, transportation, packaging and storage).Conclusions: In this work, Golab apple was considered as a viscoelastic material and its behavior under quasistatic loading was modeled using finite element method. Elastic, viscoelastic properties and shear strength of apple flesh were obtained and used in the simulation. Comparison of modeling and experimental results shows that the model simulates the behavior of apples during quasistatic loading well. The location of bruise occurrence in the flesh of tested apple and the location of maximum shear stress in the simulated apple was the same. Therefore, the maximum shear stress criterion can be used to estimate the susceptibility of apple varieties to internal bruising under quasistatic loading. Modeling of apple as a viscoelastic sphere in Abaqus software assuming constant bulk modulus could properly simulate apple behavior under quasistatic loading.
D. Ghanbarian; M. Shirvani; M. Ghasemi-Varnamkhasti; H. Golestanian
Abstract
Unfortunately despite the great ranking of Iran for apple production around the world, the export potential is not suitable. It seems that one of the major causes of poor quality for Iranian apple varieties is bruising damage of this product. Therefore, in this study, some factors affecting the apple ...
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Unfortunately despite the great ranking of Iran for apple production around the world, the export potential is not suitable. It seems that one of the major causes of poor quality for Iranian apple varieties is bruising damage of this product. Therefore, in this study, some factors affecting the apple bruising were addressed. For this purpose, factorial experiment in a completely randomized design with 72 treatments, including variety factor in three levels (Golden Delicious, Red Delicious and Granny Smith), type of padding surface in four levels (Cardboard on plastic, wood, Rubber on steel and apple) and the drop height in six levels (5, 15, 25, 35, 45 and 55 cm) with four replications were considered. Moreover, the maximum allowable drop heights of apples along with bruising volume estimation models were studied. Analysis of variance (ANOVA) showed that bruising area and volume were significantly affected by all experimental parameters at the 1% level. The comparison test revealed that Granny Smith has tougher tissues and is less prone to vulnerability. Based on the results of this study, the maximum allowable drop heights for the Red Delicious, Golden Delicious and Granny Smith varieties were found to be 12, 15 and 20 cm, respectively. In addition, the effect of apple variety on the dependent parameters was significant. Based on the findings of this study, the bruising due to the impact of apple and apple was lower for the moving apples compared with the stationary apples.
Image Processing
M. Jafarlou; R. Farrokhi Teimourlou
Abstract
Physical properties of agricultural products such as volume are the most important parameters influencing grading and packaging systems. They should be measured accurately as they are considered for any good system design. Image processing and neural network techniques are both non-destructive and useful ...
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Physical properties of agricultural products such as volume are the most important parameters influencing grading and packaging systems. They should be measured accurately as they are considered for any good system design. Image processing and neural network techniques are both non-destructive and useful methods which are recently used for such purpose. In this study, the images of apples were captured from a constant distance and then were processed in MATLAB software and the edges of apple images were extracted. The interior area of apple image was divided into some thin trapezoidal elements perpendicular to longitudinal axis. Total volume of apple was estimated by the summation of incremental volumes of these elements revolved around the apple’s longitudinal axis. The picture of half cut apple was also captured in order to obtain the apple shape’s indentation volume, which was subtracted from the previously estimated total volume of apple. The real volume of apples was measured using water displacement method and the relation between the real volume and estimated volume was obtained. The t-test and Bland-Altman indicated that the difference between the real volume and the estimated volume was not significantly different (p>0.05) i.e. the mean difference was 1.52 cm3 and the accuracy of measurement was 92%. Utilizing neural network with input variables of dimension and mass has increased the accuracy up to 97% and the difference between the mean of volumes decreased to 0.7 cm3.
R. Mirzaei; S. Minaei; M. H. Khoshtaghaza; A. M. Borghaee
Abstract
The most important quality indicator of fruits is the flesh firmness which is well correlated to their young’s modulus. In this research variation of vibration characteristics (shape modes, natural frequency) of apple due to change of material characteristics (density, young's models, Poisson ratio) ...
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The most important quality indicator of fruits is the flesh firmness which is well correlated to their young’s modulus. In this research variation of vibration characteristics (shape modes, natural frequency) of apple due to change of material characteristics (density, young's models, Poisson ratio) and apple volume was investigated using Finite Element simulation. An image processing technique was used to obtain an unsymmetrical and non-spherical geometric model of apple. The exact three-dimensional shape of the fruit was created by determining the coordinates of apple surface and forming uneven rotational curvatures. Modal analysis with no boundary constraints has been applied. The first 20 Eigen frequencies and the corresponding mode shape were determined. Six rigid body modes possess zero resonant frequency which is related to the degree of freedom of a rigid body in space indicated the validity of finite element model. The modal analysis results showed that resonant frequency increased by increasing young's modulus of the fruit, while it decreased by increasing apple density. First mode torsion has a mean resonant frequency of 584 Hz. Variations of natural frequency due to change in young's modulus, density, and Poisson ratio were 80%, 11% and 4%, respectively. Coefficient of variation of resonant frequency in response to changing young's modulus was 2-3 times of that of density which shows the greatest effect of young modulus changes on natural frequency of fruits. Consequently with determination of fruits' natural frequency, their young modulus and firmness can be estimated.
R. Tabatabaei koloor; A. Kolouri; S. J. Hashemi; R. Hadipour Rokni
Abstract
Apple fruits are subjected to different loading from harvesting to supermarket shelf. Bruising has been attracted many researchers as one of the most important damage criteria. In this research, the effects of some factors such as contact surface material, drop height and linear velocity of apples were ...
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Apple fruits are subjected to different loading from harvesting to supermarket shelf. Bruising has been attracted many researchers as one of the most important damage criteria. In this research, the effects of some factors such as contact surface material, drop height and linear velocity of apples were investigated. Influence of these factors on bruising of “Golden Delicious” variety was analyzed by a Completely Randomized Design (CRD) with factorial test at three level of drop height (10, 20 and 30 cm), linear velocity (0.05, 0.1 and 0.15 ms-1) and four contact surface (wooden, steel, plastic and cardboard). Tests were conducted at three replications with 108 treatments. Analysis of variance results showed that the effects of drop height and contact surface material on bruising area at 1% level was significant while bruising volume only affected by contact surface material (meaningful difference at 1% level). Mean comparison test indicated that there significant difference between levels of drop height on the bruise area. Also, there was a meaningful difference between contact surface of cardboard with steel, wood and plastic. There was a significant difference between surface materials of steel and wooden with cardboard and plastic. Therefore, drop height and contact surface material must be considered in designing the apple processing systems.
